Process for producing a secondary alkyl aromatic hydrocarbon and the corresponding sulfonate



United States Patent 3,337,613 PROCESS EUR PRGDUCKNG A iiEQGNDARiZ ALKYL ARGMATKC HYDRUEARBON AND THE (KORRESPONDRNG SULFGNATE Benjamin .F. Luherofi, Summit, N.i., assignor to The Lummus Company, New York, N.Y.,- a corporation of Delaware No Drawing. Filed Get. 231, i963, Ser. No. 317,776 17 Claims. (Cl. Z6-5tl5l This invention relates to a process for producing alkyl benzenes. The invention is particularly directed to alkylation of aromatics with secondary monoalkyl halides to form precursors for biodegradable secondary alkaryl sulfonates.

In recent years, a considerable demand has arisen for biodegradable sulfonates for use as detergents. Alkaryl sulfonates used to date as detergents contain highly branched alkyl groups. Such sulfonates are not readily degraded by bacteria usually encountered in Waste treatment plants and have therefore created a growing pollution problem. In contrast, unbranched secondary alkaryl sulfonates are degradable by bacteria in such waste treatment plants.

Secondary alkaryl sulfonates can be made by a sequence of operations including chlorination of suitable alkanes, generally C 41 mixtures, for the formation of secondary monoalkyl halides. Generally, chlorination is conducted to provide only a low degree of conversion in order to minimize polychlorination of the alkanes. Since mixed alkanes are used, physical separation of the secondary monochlorides from unreacted alkanes is not feasible. Instead, the partially chlorinated material is reacted with benzene or other aromatic hydrocarbons in the presence of a Friedel-Crafts catalyst under well-known, Friedel-Crafts alkylation conditions, whereby secondary alkyl aromatic hydrocarbons are formed. Unreacted alkanes are then separated by distillation for recycle to the chlorination operation. Alternatively, the reaction product containing the secondary alkyl aromatic hydrocarbons can be sulfonated and then the unreacted alkanes can be removed from the suliona-tion reaction product and recycled to the chlorination operation. However, in the chlorination step vicinal polyhalides, and particularly dihalides, are always produced together with the desired secondary monoalkyl halides. Vicinal dichlorides are particularly disadvantageous since they dehydrochlorinate in the Friedel-Crafts reaction, whereupon vinyl chlorides are formed. The vinyl chlorides are generally in admixture with unreacted alkanes separated from the secondary alkyl aromatics, and form sludges when recycled to the chlorination. The vinyl chlorides, therefore, constitute a waste product which must be removed. This invention is concerned with a process for eliminating the disadvantageous vicinal polyhalides.

It is an object of the invention, therefore, to provide a process for forming a secondary alkyl aromatic hydrocarbon. Another object of the present invention is to provide a process for preparing a secondary monoalkyl halide substantially free of an aliphatic vicinal polyhalide. Still another object of the invention is to provide a process for forming a secondary alkaryl sulfonate. A further object of the invention is to provide a. process whereby unreacted alkane used in the preparation of said alkylated aromatic hydrocarbon or in the preparation of said sulfonate, can be recycled without contamination caused by a vicinal polyhalide. Other objects of the invention will be apparent from the following description.

In accordance with the invention, the foregoing objects are realized by halogenating a saturated normal aliphatic hydrocarbon having from about 8 to about 20 carbon atoms per molecule to form a mixture predominantly comprised of a monohalide and containing a vicinal polyhalide, particularly a dihalide, of said hydrocarbon. The mixture is contacted with a material selected from (a) A polyvalent metal selected from Groups II-A, II-B and HLA of Mendeleeffs Periodic Table, either alone or in the form of a metallic couple with another metal, and

(b) An inorganic iodide.

whereby said vicinal dihalide is converted to the corresponding olefin. It is to be understood that the term polyvalent metal as used herein, including the appended claims, includes the polyvalent metal in the form of a metallic couple with another metal.

Olefins present in the hydrocarbon feed will increase the amount of vicinal dihalides in the mixture. Since the vicinal dihalides are subsequently converted to the corresponding olefin prior to alkylation, it is not necessary to use a high purity saturated aliphatic hydrocarbon feed.

An aromatic hydrocarbon and a Friedel-Crafts catalyst can be added to the reaction product containing the olefin and monochloride both of which can then be reacted with the aromatic hydrocarbon under Friedel-Crafts alkylating conditions, whereby a secondary alkyl aromatic hydrocarbon is formed. Unreacted aliphatic hydrocarbon can be separated, as by distillation, and recycled for halogenation. The reaction product containing the secondary alkyl aromatic hydrocarbon can then he sulfonated for the formation of a secondary alkaryl sulfonate. Unreacted aliphatic hydrocarbon present in the reaction product containing the desired sulfonate can be separated, as by distillation, and recycle for further chlorination.

A wide variety of saturated normal aliphatic hydrocarbons can be used in the process contemplated herein. Generally, the aliphatic hydrocarbons will contain from about 8 to about 20, and preferably from about 10 to about 16 carbon atoms per molecule. Typical alkanes include: octane, nonane, decane, dodecane, tetradecane, hexadecane, etc. In the preparation of biodegradable sulfonates of the character indicated above, generally mixtures of such hydrocarbons will be used. Particularly preferred herein are mixtures of parafiins ranging from ir le- Halogenation of the saturated aliphatic hydrocarbon or hyrocarbons can be carried out by techniques well known in the art. A guide to the extent of halogenation can be determined by the increase in the weight of the hydrocarbon material halogenated or by the amount of hydrogen chloride evolved. Generally halogenation will be continued to an extent indicative of about 5-25 percent monohalogenation of the hydrocarbon charge. While the halogens contemplated herein are chlorine and bromine, chlorine is particularly preferred. By way of illustration, temperatures of the order of about 0-75 C. are used for chlorinating the hydrocarbons. Well known catalysts for halogenation can also be used, including iodine, sun light, etc.

As indicated above, a variety of materials are used to dehalogenate a vicinal polyhalide formed during the halogenation step. Polyvalent metals of Groups II-A, II-B, and Ill-A can be used and, of such metals, zinc and aluminum are particularly preferred. Metallic couples are also advantageous in the dehalogenation step and among such materials are zinc-copper and zinc-mercury couples. So also, inorganic iodides can be used as a source of iodide ion for the dehalogenation of a vicinal polyhalide. Representative of such iodides are alkali metal and alkaline earth iodides, for example, sodium iodide and calcium iodide.

It is to be understood, of course, that all of the 'dehalogenated materials are not equivalent in their eifectiveness in converting a vicinal polyhalide to its correspondco ing olefin. Particularly advantageous for dehalogenation is zinc metal.

In the dehalogenation step, the halogenation product containing a monohalide and a vicinal dihalide is advantageously passed through a bed of granulated metal, such as zinc, or is stirred with it and filtered. Reaction temperature for this step is from about 50 C. to about 200 C., and preferably from about 100 C. to about 150 C. Contact time is continued until substantially all of vicinal polyhalide is reacted with the metal, with the resultant formation of the corresponding olefin. Generally, contact time will vary from about 0.1 to about 1 hour at the temperatures indicated. The course of this reaction can be followed by observing the increase of olefin concentration by using spectrophotometric techniques.

A particular advantage lies in the fact that metal chloride, such as zinc chloride, formed in the dehalogenation step contributes to the catalytic activity of the added Friedel-Crafts catalyst, viz, AlCl in a subsequent Friedel-Crafts alkylation of an aromatic hydrocarbon.

When an inorganic iodide is used as a dehalogenation aid, the chlorination reaction product can be intimately contacted with an aqueous solution of the inorganic iodide and can then be dried. Reaction temperature for the latter operation will range from about 20 C. to about 100 C., preferably 50 C. to 80 C. An iodide solution having an iodide concentration ranging from about 1 to about 20 percent, by weight, is advantageous. Free iodine formed in such a dehalogenation can be recovered, for example by extraction into carbon tetrachloride.

In the formation of a secondary alkyl aromatic hydrocarbon, numerous aromatic hydrocarbons can be used. Representative of such hydrocarbons are benzene, toluene, xylenes, naphthalene, methyl naphthalenes, anthracene, etc. Particularly preferred herein is benzene. Mixtures of aromatic hydrocarbons, of substituted aromatic hydrocarbons and of substituted and non-substituted aromatic hydrocarbons, can be used.

An excess of aromatic hydrocarbon is used in order that polyalkylation, particularly di-alkylation, is avoided or is minimized.

In the alkylation of the aromatic hydrocarbons with the monohalide and with the olefin formed from the vicinal dihalide, any of the well known Friedel-Crafts catalysts can be utilized. Included among such catalysts are aluminum chloride, ferric chloride, stannic chloride, boron trifiuoride, zinc chloride and hydrogen fluoride. Preferred, however, is aluminum chloride. Alkylating conditions used in this operation are the well known Friedel-Crafts alkylation conditions.

Sulfonation of a secondary alkyl aromatic hydrocarbon or mixture of two or more of such hydrocarbons, can be accomplished with any of the well known sulfonation agents. Sulfur trioxide, chlorosulfonic acid, and sulphuric acid of various strengths can be used. Here also, conditions for sulfonation are of those customary in the art. Temperatures can range from about C. to about 150 C., with preference given to temperatures of 100C. The quantity of sulfonation agent can be suflicient to provide essentially a monosulfonate or can be greater in order that a substantial amount of disulfonate is formed.

It is emphasized herein that sludges and waste materials hitherto formed by virtue of contamination caused by a vicinal dihalide being carried through the processing techniques indicated above, are avoided. Thus unreacted paraffin present in the reaction mixture containing a secondary alkyl aromatic hydrocarbon, or present in the reaction mixture containing a secondary alkaryl sulfonate, can be separated from said reaction product and returned to the chlorination step for further use. Thus, there is no contamination caused by a vicinal polyhalide as has characterized prior halogenation processes followed by alkylation and/ or alkylation and sulfonation. For example, if 5 percent of an alkane is converted to a vicinal lowing composition: Percent Weight One hundred parts by weight of the mixture are chlorinated by passing a stream of chlorine gas through it at a temperature of about 50 C. until the gain in weight is about 2 percent, at which time about 0.5 mole of HCl will have been evolved per kilogram of hydrocarbon. The reaction product comprises monochlorides, and some polychlorides including vicinal dichlorides, and unreacted Cm-Cw parafiins. The chlorination reaction product is then stirred with one hundredth part of weight of finely powdered, clean zinc metal at about C. for about 0.5 hours, whereupon the vicinal dichlorides present in the reaction product are dechlorinated to the corresponding olefins. At the same time, zinc chloride is formed. Benzene, 50 parts by Weight, and aluminum chloride, 10 parts by weight, are now added to 100 parts of the product of the dechlorination step. A Friedel-Crafts alkylation is accomplished at refiux for about 2 hours, resulting in the formation of a mixture of secondary alkyl (c c benzenes. Inorganic material present in the Friedel-Crafts reaction product is removed by washing with water and separating the organic phase which is filtered through a filter aid such as a diatomaceous earth. Unreacte-d benzene and the unreacted paraffins present in the Friedel-Crafts reaction product, are removed therefrom by distilling the product. The paraffins so recovered are free from vinyl chlorides, and are suitable for chlorination. The filtrate is distilled to recover the desired secondary alkyl (C -C benzenes. The alkyl benzenes can then be sulfonated to the corresponding monosulfonates.

While the invention has been described in detail according to preferred compositions and preferred processes for using the same, it will be obvious to those skilled in the art that changes and modifications can be made without departing from the spirit or scope of the invention and it is intended in the appended claims to cover such changes and modifications.

I claim:

1. A process for producing a secondary alkyl aromatic hydrocarbon comprising:

(a) reacting a saturated normal aliphatic hydrocarbon having from about 8 to about 20 carbon atoms per molecule with a halogen selected from the group consisting of chlorine and bromine to produce a mixture containing a monohalide and a vicinal dihalide of said hydrocarbon;

(b) contacting said mixture with a material selected from the group consisting of (l) a polyvalent metal selected from the group consisting of the polyvalent metals of Groups II-A, II-B, III-A of Mendeleefis Periodic Table; and

(2) an inorganic iodide to convert the vicinal dihalide to the corresponding olefin;

(c) adding an aromatic hydrocarbon and a Friedel- Crafts catalyst to the reaction product formed in (b); and

(d) reacting said monohalide, said olefin and said aromatic hydrocarbon under Friedel-Crafts alkylating conditions, whereby a secondary alkyl aromatic hydrocarbon is formed.

2.. The process of claim it wherein said material of step (b) is an alkali metal iodide.

3. The process of claim 2 wherein said contacting is effected at a temperature between about 20 C. and about 100 C.

4. The process of claim 3 wherein said halogenation is effected at a temperature between about and about 75 C.

5. The process of claim 4 wherein said alkali metal iodide is sodium iodide and said aromatic hydrocarbon is benzene.

6. The process of claim 5 wherein the secondary alkyl aromatic is sulfonated to produce a secondary alkaryl sulfonate.

7. The process of claim 1 wherein said material of step (b) is a polyvalent metal as defined in (1).

8. The process of claim 7 wherein the contacting of step (b) is effected at a temperature between about 50 C. and about 200 C.

9. The process of claim 8 wherein the halogenation is efiected at a temperature between about 0 C. and about 75 C.

10. The process of claim 9 wherein the aromatic hydrocarbon is benzene.

11. The process of claim 10 wherein the secondary alkyl aromatic is sulfonated to produce a secondary alkaryl sulfonate.

12. The process of claim 10 wherein the polyvalent metal is zinc.

13. The process of claim 10 wherein the polyvalent metal is aluminum.

14. The process of claim 1 wherein the halogenation is eifected at a temperature between about 0 and about 75 C. and the aromatic hydrocarbon is benzene.

15. The process of claim 14 wherein the material of References Cited UNITED STATES PATENTS 1,248,065 11/1917 Blanc 260-660 X 1,384,447 7/ 1921 Gardner et a1. 260-677 2,161,174 6/1939 Kyrides 260-605 2,495,323 1/1950 Gisl-on 260-671 FOREIGN PATENTS 612,036 4/1962 Belgium.

OTHER REFERENCES Fieser et al.: Organic Chemistry, 1944 (Boston), 59-60. Pressman et al.: J. A. Chem. Soc., vol. 66 (May 1944), 705-709.

Schubert et al.: J. A. Chem. Soc., vol. 74 (Sept. 20, 1952), 4590-2.

Schwartz et al.: Surface Active Agents and Detergents, vol. II, 1958 (New York), 79.

LORRAINE A. WEINBERGER, Primary Examiner. M. B. WEBSTER, Assistant Examiner. 

1. A PROCESS FOR PRODUCING A SECONDARY ALKYL AROMATIC HYDROCARBON COMPRISING: (A) REACTING A SATURATED NORMAL ALIPHATIC HYDROCARBON HAVING FROM ABOUT 8 TO ABOUT 20 CARBON ATOMS PER MOLECULE WITH A HALOGEN SELECTED FROM THE GROUP CONSISTING OF CHLORINE AND BROMINE TO PRODUCE A MIXTURE CONTAINING A MONOHALIDE AND A VICINAL DIHALIDE OF SAID HYDROCARBON; (B) CONTACTING SAID MIXTURE WITH A MATERIAL SELECTED FROM THE GROUP CONSISTING OF (1) A POLYVALENT METAL SELECTED FROM THE GROUP CONSISTING OF THE POLYVALENT METALS OF GROUPS II-A, II-B, III-A OF MENDELEEFF''S PERIODIC TABLE; AND (2) AN INORGANIC IODIDE TO CONVERT THE VICINAL DIHALIDE TO THE CORRESPONDING OLEFIN; (C) ADDING AN AROMATIC HYDROCARBON AND A FRIEDELCRAFTS CATALYST TO THE REACTION PRODUCT FORMED IN (B); AND (C) REACTING SAID MONOHALIDE SAID OLEFIN AND SAID AROMATIC HYDROCARBON UNDER FRIEDEL-CRAFTS ALKYLATING CONDITIONS, WHEREBY A SECONDARY ALKYL AROMATIC HYDROCARBON IS FORMED. 